| In order to reduce the worldwide incidence of iodine deficiency disorders (IDD), and to prove the supplementation of iodine in food chain through plant uptake to improve human nutrition, a series of experiments and research were conducted. Furthermore, with the rapid development of nuclear industry in China, there is an urgent need to characterize I chemistry in different soils. The objectives of this research were (1) to investigate iodate and iodide ad-desorption by various soils from China; (2) to identify principal factors controlling iodate and iodide ad-desorption in soil; (3) to select iodine-riched vegetable for efficient iodine accumulation, and to examine the residual effect of soil application iodine-containing fertilizers; (4) to investigate the bioavailability of iodide and iodate to spinach in soil and iodine concentration in soil solution; (5) to confirm the effect of iodine on spinach quality, and ultimately to assist in establishing guidelines for incorporating iodate from soil to vegetables, then into the human food chain. The results were as follows: Ion chromatography coupled with pulsed amperometric detection was used to determine iodide in solution. This method was specific, sensitive and rapid, the detection limit of iodide was 0.31?g L-1(S/N=3),recovery with adding standard was 99.86%? A series of experiments were conducted to assess the adsorption of iodate and iodide by different soils from China. Iodate and iodide adsorption isotherms could be well fitted with both Langmuir and Freundlich equations. It was found that soils rich in free iron oxide had high affinity for iodate. Iodate adsorption by 20 different soils from China revealed that iodate adsorption was significantly correlated with soil organic matter negatively, and positively with free iron oxide contents. At initial concentration of 4 mg I L-1, iodate adsorption ranged from 9 to 34 mg kg-1 soil. No correlations between iodate adsorption and cation exchange capacity and soil pH were found. For a single soil, there was a significant linear relationship between the amounts of iodate adsorbed and desorbed, but for a group of soils, the relationship between the amounts of iodate adsorption and desorption followed a nonlinear relationship, the deviation mainly occurred at high adsorption side. The relationship between Kd and free aluminum oxide and free iron oxide contents showed an exponential relationship for various soils with exception of the soil of Hetian in Xinjiang. It was found that soils rich in organic matter and with high cation exchange capacity had high affinity for iodide. Iodide adsorption by 17 different soils from China revealed that iodide adsorption was significantly correlated with cation exchange capacity and soil organic matter positively. At initial concentration of 4 mg I L-1, iodide adsorption ranged from 0.782 to 6.593 mg kg-1 soil. No correlations between iodide adsorption and free aluminum/iron oxide and soil pH were found. For a single soil and a group of soils, there was a significant linear relationship between the amounts of iodide adsorbed and desorbed. The relationship between Kd and cation exchange capacity and soil organic matter showed a significant linear relationship for 17 various soils. A greenhouse pot experiment was conducted to select efficient vegetables for iodine uptake, and to investigate the effects of iodate application to soil on iodine uptake by vegetables. The residual effect of iodate fertilization on the growth of and iodine uptake by spinach plants was also investigated. Six vegetables including leafy vegetables, tuber vegetables, shoot vegetables and root vegetables were examined. Results showed that the concentrations of iodate in soil had significant effect on the biomass of edible parts of pakchoi and spinach (P<0.01), whereas the concentrations of iodate in soil had no significant effect on that of carrot, waterspinach, celery and onion. Iodine concentrations in edible parts of vegetables and the transfer factors (TFedible parts) of soil-to-ed... |
PDF Full Text Request